[Excaliber]

The higher the octane the gas is the less likely run on will occur. High octane fuel is actually harder to ignite than low octane is. That is the fundamental difference between the high and low, one is more stable than the other.

Running race gas, extreme octane? Run on won't be a problem.

David that an interesting observation about the timing effect. Of course once you turn off the key it doesn't matter where the timing used to be, it aint there anymore at all. So, what could be happening with reduced timing not promoting run on? Possibly a cleaner burning combustion chamber or a slightly cooler combustion chamber by "just enough".